1. Field of the Invention
The present invention relates to an ink composition, an ink set, and a recording method, in particular, relates to an ink composition capable of forming an image having high fastness and high density.
2. Description of the Related Art
With the spread of the computer in recent years, ink jet printers have been widely used not only in offices but also in homes for printing on papers, films and cloths.
As ink jet recording methods, a method of ejecting ink droplets by applying pressure by piezo-elements, a method of ejecting ink droplets by generating bubbles in ink by heat, a method of using ultrasonic waves, and a method of suction ejection of ink droplets by electrostatic force are known. As the ink compositions for these ink jet recordings, water ink, oil ink and solid ink (a melting type) are used. Of these inks, water ink is mainly used for easiness of manufacture and handling, odors and safety.
Colorants used in inks for these ink jet recordings are required to have high solubility in solvents, to be capable of high density recording, to be good in hue, to be excellent in fastness to light, heat, air, water and chemicals, to have good fixing property to image-receiving materials and to hardly blot, to be excellent in preservation property as inks, to be free of toxicity, to be high in purity, and to be available inexpensively. However, it is extremely difficult to search for colorants that satisfy these requirements in high levels.
Various dyes and pigments have been already proposed for ink jet recording and practically used but colorants satisfying all of these requirements have not been discovered yet. It is difficult for conventionally known dyes and pigments having Color Index Nos. (C.I.) to reconcile the hue and fastness required of the inks for ink jet recording.
Tris-azo dyestuffs and tetrakis-azo dyestuffs are discussed in recent years as the dyes for black inks and disclosed in JP-A-2005-220211 (the term “JP-A” as used herein refers to an “unexamined published Japanese patent application”), JP-A-2004-28535 1, JP-A-2005-2271 and WO 03/106572, but these dyestuffs do not come to sufficiently satisfy the demands of the market, in particular on the fastness to gases and lights.
The present inventors have continued the examination of dyes good in hue and fastness and the development of dyes excellent for ink jet recording. From these examinations, it has been found, as disclosed in JP-A-2005-162823, that it is effective to use a dye high in association to increase fastness of images.
However, it has also been found that, when a dye having an associating property is used, there arise problems of liability to bronzing (abnormal glossiness) at the high concentration area, and the reduction of image density as compared with a dye not having an associating property.